Protection switching is an essential feature in microwave and millimeter wave radio systems to meet system reliability objectives. There exist many different methods and systems to achieve an increase in system reliability and availability of protection switching. For example, a typical protection switching architecture may be realized as redundant sets of modules that are subparts of a higher level component and implement functions of the component. The component may be structured and controlled such that there are redundant modules for each feature or group of features of importance. In such an architecture there generally are at least two modules which implement each important function. These modules are typically referred to as redundant modules or redundant module sets. Prior art protection switching is generally constructed of one or more sets of these redundant modules, the premise being if a currently selected set fails, one other unselected set may be promptly substituted for the failed set and the component can resume providing communication or the relevant function.
A methodology and mechanism is required to control and communicate information regarding control of which of the redundant sets is the active or standby set. When this function is structured to operate without intervention of separate equipment or entities, it is commonly referred as automatic protection switching. In prior art radio systems, these switching decisions are generally made by a central controller. For example, prior art radio systems typically utilize a single central controller responsible for the control of protection switches based upon component and path alarms collected from various modules in a system. As a result, when the controller fails, no further switch decisions may be made, and the corresponding protection switch is frozen at its last state. Thus, any further component, equipment or path failures may result in a traffic or communication outage. Further, prior art mechanisms utilized to communicate with the central controller and any queuing associated therewith add delay in the reconfiguration of the component or equipment. Therefore, it is desirable to realize protection switching as a distributed solution so that communication may be protected from single failures.
Typical prior art automatic protection systems for network elements have also generally comprised, for example, redundant facility equipment wherein a detected failure in one of the redundant sides results in a switch from one redundant side to the other. In such an architecture, an entire line of protection equipment is substituted for another even if a failure occurred in only one place in the working channel. Such an approach is inflexible since it fails to maximize available equipment. Moreover, switching decisions are typically made by the system controller, and all information relevant to the protection switching decision must still be sent to the system controller. Since the system controller services all information in this type of architecture, a significant amount of time is required to accomplish the switchover, and all the elements on the data path are still required to be switched during a switching event.